The use of electrolytic cells for the production of metal by the reduction of a metal halide in a molten salt electrolyte has been known for many years. That the process requires large amounts of electrical energy has been recognized and accepted for almost as many years. The high cost of electrolysis due to high consumption of electrical energy is a problem that has been the subject of much research.
A cell of the well-known type, useful for the production of either zinc or lead by the reduction of the appropriate metal chloride, is described in U.S. Pat. No. 1,545,383 to Ashcroft. The cell includes a group of closely spaced, inclined graphite plates which function as bipolar electrodes arranged in a superimposed, spaced relationship to define inter-electrode spaces. As electrolysis proceeds, metal and chlorine are produced in the inter-electrode spaces. Because of the inclination of the electrodes, the metal produced in the cell flows downwardly across the cathode surfaces of intermediate electrodes, while at the same time, the chlorine produced flows upwardly across the inclined anode surfaces of intermediate electrodes and through holes near the ends thereof to a gas-collecting zone in the top of the cell. The anode and cathode surfaces of the electrodes of this cell may be corrugated or grooved in the direction of the flows of metal and chlorine in the cell. Nonetheless, the chlorine gas must traverse the surface of the anode and, therefore, the length of the intra-electrode electrolyte bath area before it reaches the holes leading to the gas-collecting zone.
This presence and build-up of gas generated during electrolysis has long been recognized as one of the major causes of the large electrical energy requirements of electrolytic cells. For example, U.S. Pat. No. 1,856,663 to Smith describes a multiple electrode for electrolytic apparatus which conducts or directs the generated gases away from the electrolyzing area. The electrode includes interconnected, superposed electrode elements provided with a flat central portion and upwardly pointed angular corrugations or flutings along their electrolyzing edges which, when assembled, form a plurality of vertical central and side passages.
In further attempts to achieve efficient electrolysis by removing generated gases, there have been developed various other designs and arrangements of electrodes for use in electrolytic cells. U.S. Pat. No. 4,151,061 to Ishikawa et al describes a "funnel-shaped" electrode element arrangement formed of at least three vertically stacked electrodes inclined downwardly and inwardly, having a first communicating passage formed in the center and a second communicating passage formed between the outer edge of the electrodes and the inner wall of the cell. Other electrode configurations are disclosed by U.S. Pat. No. 4,401,530 to Clere and U.S. Pat. No. 2,959,533 to de Varda.
It is clear from the above-noted prior art that in order to efficiently electrowin metal from an electrolyte bath in an electrolytic cell, the electrodes must be appropriately designed and positioned. Despite this knowledge, the electrolytic production of lead from an electrolytic bath still requires a consumption of electricity which remains very large and, consequently, the process is very expensive. The problem with the noted known electrolytic cell electrode assemblies is that effective, rapid removal of gas generated during electrolysis is still not achieved nor is the effective electrolyte bath area between the electrodes maximized by maximizing the electrode surface area. Consequently, electrolytic production of metal remains inefficient and costly. Therefore, it would be advantageous if the consumption of electricity could be limited by an efficient and effective electrode assembly. To produce lead efficiently and inexpensively, unlike the electrode designs of the above-cited prior art, the electrode assembly should rapidly and effectively direct the gas produced away from the effective electrolytic bath area between the electrodes, increase both the effective electrolytic bath area and the electrode surface area and permit the metal produced to accumulate in another portion of the cell.
There is a need for an electrode assembly for use in electrolytic cells which enables the efficient, inexpensive production of metal from the appropriate metallic molten salt bath.